The hardness test is a process or method used to measure the hardness of different materials. In simple words, the hardness of any material refers to its level of resistance to permanent indentation.
There are many different techniques to measure the hardness of numerous materials, and each test can give different results of the same material.
Because every test is designed to measure the hardness of specific materials. And every material has different physical properties from other materials. If you use the same test for every material, then you will get the wrong findings.
In the era, everything is made from plastic, and usage of plastic is growing on a daily basis.
It is very important to measure the hardness of the plastic, without knowing the hardness level of the material you can’t assure its quality if you want to meet the expectations of your customers then the material quality should be very high.
Types of plastic:
Quality of any material used in manufacturing goods is very important, and if the material you use is of low quality, then it will affect the performance.
Raw plastic has many different shapes and types, and the test is depended on the form of plastic that you want to test. In basic term, there is two variable used in plastic, cure, and mix. Hardness testing can be easily done on both variables to verify them.
The plastic materials that are commonly used in hardness testing are the molded parts and plastic sheets.
There some other forms of plastic such as thermos-polystyrene, cellulose acetate, Formica, thermos- plastics and Plexiglas are common for hardness testing of plastic.
Hardness testing for plastic:
Hardness testing for the plastic is very simple, in hardness testing for plastic an external force is applied on it to check its resistance.
In this testing, the force is applied with the help of the indenter at the center of the sample material. The indenter is pushed into the plastic in certain motion with the specific force until the presser foot touched the plastic.
It is the time to measure the depth of the indenter on the sample material, how far does indenter penetrates the plastic.
Through this process, you will calculate the level of resistance of that plastic sample. The resistance to the indenter of this penetration can be of plastic mixer or cure.
If the indenter deeply penetrated in the plastic material, then it is termed as the soft plastic, and if the indenter failed to penetrate in the plastic, then it is extremely hard plastic. You can easily calculate the hardness level by measuring the indenter depth. It is a common and very simple method of testing the hardness of the plastic.
Cause of hardness testing failure:
There are many reasons that the hardness testing of the plastic failed to give the correct results. Hardness testing is very easy and simple but require the proper training to perform the test.
Sometimes the professional test performers failed to achieve the correct result due to minor mistakes.
The hardness testing of the plastic may be failed due to several reasons such as tester applied too much load than required or his setup of testing is incorrect. If you use the wrong types of the indentation device, then you will get the wrong findings.
Every test is designed for the specific materials, and it is very important to use the right test according to the nature of your material.
As we have discussed above, plastic has many forms and types, even the thickness of the plastic can affects the results. If you select the thin sample of hard plastic in the indentation method, you will definitely get the incorrect results.
Types of hardness test for plastic:
There are three different types of hardness test used for testing the hardness of the plastic. In the scientific term, these three hardness tests are D2240, ASTM D785, and E384/E92. In the general terms, these three tests are known as shore- durometer-hardness, Rockwell hardness, and Knoop & Vickers test.
The above three tests are used according to the different testing standards in every country. Even the companies have their own choice of the hardness testing method as per their quality standards.
The most common method of testing the hardness of the plastic used in worldwide is the Rockwell hardness method. ASTM hardness method is used in the United States, and they prefer this testing for every product, whether it is imported or for export. Rockwell hardness testing is known for the higher standard materials.
Rockwell hardness test:
In the Rockwell hardness test, the ball indenter is used to penetrate in the plastic to know its resistance. In common test, the ball indenter with the force range from 15 to 150 kg is used.
The ball with the diameter of 1/8-, ¼- and ½- inch indenters are used. The Rockwell test for the plastic is the same as the normal test for the plastic hardness test. There is the only difference between dwell and recovery time due to the characteristics of the plastic.
The uniqueness of plastic testing:
There are many different materials used in the production process; most of them have similar physical properties and have the same testing criteria. Testing of the plastic is unique than other materials because plastic has different viscoelasticity and time-dependent effects. These things must be considered before measuring the hardness of the plastic.
Analyze the tests:
For testing the hardness of the plastic, there are many different options available, and you can choose according to your standards. In this era of technology, everything is controlled by computer systems.
The latest technology contributes a lot to the testing procedure and makes them easy with the exact results. In testing the hardness of the plastic, the mostly testers used the computer-controlled amount of load on the sample material.
The time and the load is controlled by the computer, and you can set the duration and the load amount manually or can use the different software to set the duration and weight automatically according to the type of sample material.